In automatic letter sorting systems, it is necessary for different applications to determine the weight of flat, flexible objects which tear easily and which have different lengths, e.g., C6 letters, DL letters, C5 letters, postcards, these objects are transported as a continuous stream, without stopping or delaying the objects. Difficulties can arise in that, the weight of the mail items must also be determined accurately and reliably when the mail items are transported at high speeds, e.g., above a speed of 2 m/s. Even at these speeds, the mail items must not be damaged. In addition, it is necessary that the mail items largely maintain their relative position with respect to one another in the continuous stream. In particular, the weight determination should not change the gaps between the mail items.
Methods have already been disclosed wherein the objects to be weighed are guided horizontally over a weighing system and are weighed dynamically during this process. At higher speeds, however, displacements occur between the objects because the objects are not firmly grasped by the conveying system; moreover, these arrangements do not allow high throughputs because, with small distances between the objects the individual objects do not remain in the weighing system long enough to determine the weight with sufficient accuracy. If there are only small gaps between objects of different lengths, the result is that short objects are not disposed in the weighing system by themselves, so that, in these cases, it is not possible to determine the weight of the small objects at all. To solve this problem, the stream of objects can be split into several partial streams and the individual objects fed to several weighing systems. In principle, this permits a higher overall throughput. However, the problem continues to exist that the individual objects of the partial streams can be displaced, so that such arrangements cannot be used for higher speeds. Furthermore, there is the risk that the objects to be weighed get damaged during the transition to the weighing system, especially if they are not rigid and stable enough.